Not Applicable.
Not Applicable.
1. Field of the Invention
The present invention relates to devices for handling coiled tubing. More particularly, the present invention relates to coiled tubing handling devices that hold at least two reels of coiled tubing. Still more particularly, the present invention relates to coiled tubing handling systems that use a conveyor to direct coiled tubing to and from at least two reels.
2. Description of the Related Art
Coiled tubing, as currently deployed in the oil field industry, generally includes small diameter cylindrical tubing having a relatively thin wall made of metal or composite material. Coiled tubing is typically much more flexible and of lighter weight than conventional drill pipe. These characteristics of coiled tubing have led to its use in various well operations. For example, coiled tubing is routinely utilized to inject gas or other fluids into the well bore, inflate or activate bridges and packers, transport well logging tools downhole, perform remedial cementing and clean-out operations in the well bore, and to deliver or retrieve drilling tools downhole. The flexible, lightweight nature of coiled tubing makes it particularly useful in deviated well bores.
Typically, coiled tubing is introduced into the oil or gas well bore through wellhead control equipment. A conventional handling system for coiled tubing can include a reel assembly, a gooseneck, and a tubing injector head. The reel assembly includes a rotating reel for storing coiled tubing, a cradle for supporting the reel, a drive motor, and a rotary coupling. During operation, the tubing injector head draws coiled tubing stored on the reel and injects the coiled tubing into a wellhead. The drive motor rotates the reel to pay out the coiled tubing and the gooseneck directs the coil tubing into the injector head. Often, fluids are pumped through the coiled tubing during operations. A rotary coupling provides an interface between the reel assembly and a fluid line from a pump. Such arrangements and equipment for coiled tubing are well known in the art.
While prior art coiled tubing handling systems are satisfactory for coiled tubing made of metals such as steel, these systems do not accommodate the relatively long spans of drill or working strings achievable with coiled tubing made of composites. Such extended spans of composite coiled tubing strings are possible because composite coiled tubing is significantly lighter than steel coiled tubing. In fact, composite coiled tubing can be manufactured to have neutral buoyancy in drilling mud. With composite coiled tubing effectively floating in the drilling mud, downhole tools, such as tractors, need only overcome frictional forces in order to tow the composite coiled tubing through a well bore. This characteristic of composites markedly increases the operational reach of composite coiled tubing. Thus, composite coiled tubing may well allow well completions to depths of 20,000 feet or more, depths previously not easily achieved by other methods.
Moreover, composites are highly resistant to fatigue failure caused by xe2x80x9cbending events,xe2x80x9d a mode of failure that is often a concern with steel coiled tubing. At least three bending events may occur before newly manufactured coiled tubing enters a well bore: unbending when the coiled tubing is first unspooled from the reel, bending when travelling over a gooseneck, and unbending upon entry into an injector. Such accumulation of bending events can seriously undermine the integrity of steel coiled tubing and pose a threat to personnel and rig operations. Accordingly, steel coiled tubing is usually retired from service after only a few trips into a well bore. However, composite coiled tubing is largely unaffected by such bending events and can remain in service for a much longer period of time.
Hence, systems utilizing composite coiled tubing can be safely and cost-effectively used to drill and explore deeper and longer oil wells than previously possible with conventional drilling systems. Moreover, completed but unproductive wells may be reworked to improve hydrocarbon recovery. Thus, composite coiled tubing systems can allow drilling operations into territories that have been inaccessible in the past and thereby further maximize recovery of fossil fuels.
However, these dramatic improvements in drilling operations cannot be realized without handling systems that can efficiently and cost-effectively deploy extended lengths of composite coiled tubing. Prior art coiled tubing handling systems do not readily accommodate the frequent reel change-outs needed when injecting thousands of feet of coiled tubing downhole. Prior art coiled tubing handling systems require a work stoppage to change out an empty reel for a full reel. Because such a procedure is inefficient, there is a need for a coiled tubing handling system that more efficiently changes-out successive reels of coiled tubing.
The present invention overcomes the aforementioned deficiencies of the prior art by providing a system that utilizes multiple reel assemblies that provide enhanced operational efficiencies with respect to prior art reel assemblies. A multiple reel assembly made in accordance with the present invention includes a coaxial arrangement of multiple reels arranged side-by-side on a common platform. In such an arrangement, coiled tubing can be injected from two or more reels successfully without requiring a work stoppage for a reel change-out. A conveyor is used to direct coiled tubing from the reels to a gooseneck or injector head. In one embodiment, a spent reel is slid axially and replaced by a fresh reel. In this embodiment, the conveyor remains generally stationary. In another embodiment, the reels remain generally stationary and the conveyor pivots to accommodate the changing direction of the travel of the coiled tubing. Thus, the present invention comprises a combination of features and advantages that enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings.